Overview The production of genetically-modified mouse models and antibody reagents has revolutionized biomedical research (1-4). These research tools have made it possible to answer many questions that cannot be addressed otherwise, and have helped to define the roles of specific gene products in complex processes such as adipogenesis and obesity, diabetes mellitus, and plasma lipid metabolism. The principal objectives of the Mouse Model and Antibody Core of this Program Project Grant (PPG) are to generate gene-targeted mice and to prepare both monoclonal and polyclonal antibodies for the three projects. Genetically modified mouse models and polyclonal or monoclonal antibodies will be used in all three projects. It is both expensive and time consuming to generate new lines of mice and to create antibodies, and both require considerable technical expertise. Even though mouse and antibody reagents are critical for many modern biomedical research projects, it is very difficult for the majority of laboratories to keep the requisite techniques "up in the air" at all times. Often, the required technical expertise disappears when a technician leaves for another institution or a postdoctoral fellow departs for a faculty position. It is then inefficient, expensive, and painful to re-establish the techniques within the laboratory. Therefore, it makes sense, particularly for a PPG, to centralize these functions within a core facility. In this PPG, we are fortunate to inherit the technical expertise of BayGenomics personnel (Drs. Fong, Young, Reue, Hu) in creating genetargeted mice, and the substantial experience of Drs. Bensadoun, Fong, and Young in the production of monoclonal and polyclonal antibodies.